Explanation From HCIA-Security documents:

AAA provides a unified framework for Authentication, Authorization, and Accounting, and on Huawei devices the AAA authentication method can be selected according to the management and deployment requirements. Local authentication uses user accounts stored on the device itself, which is suitable for small environments, emergency access, or when external servers are unavailable. RADIUS authentication relies on a centralized RADIUS server, commonly used for large-scale user access control and unified credential management. HWTACACS authentication is another centralized mode that supports fine-grained control and is often preferred in scenarios requiring stronger separation of authentication and authorization, as well as detailed command-level management in some deployments. In addition, AAA can be configured for no authentication (also called none), meaning the device does not verify user identity for a specific access scenario. This mode is typically used only in controlled environments or for specific services where authentication is handled elsewhere, because it reduces security. Therefore, all listed modes are supported by AAA.

Application-layer protocols provide network services directly to user applications and define how clients and servers exchange application data. DNS is an application-layer protocol used to translate domain names into IP addresses (and perform related record lookups), enabling applications to locate services by name instead of by numeric address. Telnet is also an application-layer protocol that provides remote terminal access; it allows a user to interact with a remote system’s command-line interface over the network (though it is insecure because it transmits data in plaintext). HTTP is an application-layer protocol used for web communication, defining request/response behavior between browsers (clients) and web servers for transferring web pages and related content.

In contrast, ARP is not an application-layer protocol. ARP operates at the boundary of Layer 2/Layer 3 to map an IPv4 address to a MAC address on the local network segment, supporting frame delivery on Ethernet. Therefore, the application-layer protocols here are DNS, Telnet, and HTTP.

Explanation From HCIA-Security documents:

All four statements describe standard PKI roles and structure. A PKI entity is any certificate holder or relying participant that uses PKI services, which includes people, organizations, network devices, servers, and even application processes, so A is correct. PKI trust is commonly built using a CA hierarchy, where the root CA anchors trust and subordinate CAs issue certificates under the root’s authority, so B is correct. The CA is the core trusted component that signs (issues) certificates and manages their lifecycle activities such as renewal, suspension or revocation publication, and certificate status services, so C is correct. In many enterprise implementations, the PKI system is presented as three major roles: entities that request/use certificates, the RA that performs identity verification and approval of requests, and the CA that issues certificates based on validated requests, so D is also correct.

On a firewall that includes antivirus inspection, the device can take different response actions after it detects malware in traffic (for example, in file transfers, email attachments, or web downloads). Block is a standard antivirus action: the firewall stops the session or drops the infected content to prevent the malicious file from reaching the destination host. Alert (alarm/log) is also a common response action: the firewall generates an event, log, or alarm so administrators can investigate the source, destination, file type, signature name, and policy that triggered the detection.

Some firewall antivirus engines also support content-handling actions such as deleting an attachment (or stripping the infected file/attachment) while allowing the rest of the session to proceed, depending on the protocol and security profile. This is typically used in scenarios like email or file-based protocols where removing the infected payload is feasible.

Declare is not a normal antivirus response action on firewalls; it does not describe a meaningful enforcement or notification behavior. Therefore, the valid antivirus response actions here are Block, Alert, and Delete attachment.

Huawei firewalls use security zones to group interfaces that share the same trust level and security policy requirements. In the default configuration, Huawei firewalls provide four built-in zones that cover the most common deployment scenarios.

Trust represents the internal network where users and servers are typically considered more reliable. Untrust represents external networks such as the Internet, where traffic is considered untrusted and usually requires stricter access control and security inspection. DMZ is designed for semi-public servers (for example, web or mail servers) that must be reachable from Untrust but should be isolated from the Trust network to reduce lateral movement risk if a DMZ host is compromised. Local is a special zone that represents the firewall device itself (management plane and control plane). Traffic destined to or originating from the firewall (such as management access, routing protocol packets, or local services) is associated with the Local zone and is controlled using dedicated policies.

Because these four zones are pre-defined and available by default, all listed options are correct.

Explanation From HCIA-Security documents:

IKE-based SA establishment is designed to automate IPsec parameter negotiation and key management, which makes it especially suitable for environments where configuring many tunnels manually would be inefficient. That is why B is correct: IKE scales better for medium and large networks because it negotiates policies, authenticates peers, and builds SAs dynamically instead of relying on fixed, manually configured keys.

A is incorrect because Security Associations have lifetimes. Both IKE SAs and IPsec SAs are created with time-based and/or traffic-based lifetimes and must be refreshed or renegotiated when they expire to maintain security. Permanent SAs would increase risk because long-lived keys are more exposed to compromise.

C is correct : SPI is a 32-bit identifier used by the receiver to find the correct SA for inbound traffic, and it is typically chosen by the receiving side in a way that avoids collisions—commonly treated as randomly generated in foundational descriptions.

D is correct because IKE uses Diffie-Hellman to derive shared keying material securely over an untrusted network, and then refreshes keys by rekeying based on SA lifetime, achieving dynamic updates.